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Push-Based Security Event Token (SET) Delivery Using HTTP
RFC 8935

Document Type RFC - Proposed Standard (November 2020)
Authors Annabelle Backman , Michael B. Jones , Marius Scurtescu , Morteza Ansari , Anthony Nadalin
Last updated 2020-11-30
RFC stream Internet Engineering Task Force (IETF)
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Additional resources Mailing list discussion
IESG Responsible AD Benjamin Kaduk
Send notices to (None)
RFC 8935
quot; [RFC7525] MUST be followed.

5.4.  Denial of Service

   The SET Recipient may be vulnerable to a denial-of-service attack
   where a malicious party makes a high volume of requests containing
   invalid SETs, causing the endpoint to expend significant resources on
   cryptographic operations that are bound to fail.  This may be
   mitigated by authenticating SET Transmitters with a mechanism such as
   mutual TLS.  Rate-limiting problematic transmitters is also a
   possible means of mitigation.

5.5.  Authenticating Persisted SETs

   At the time of receipt, the SET Recipient can rely upon TLS
   mechanisms, HTTP authentication methods, and/or other context from
   the transmission request to authenticate the SET Transmitter and
   validate the authenticity of the SET.  However, this context is
   typically unavailable to systems to which the SET Recipient forwards
   the SET, or to systems that retrieve the SET from storage.  If the
   SET Recipient requires the ability to validate SET authenticity
   outside of the context of the transmission request, then the SET
   Recipient SHOULD ensure that such SETs have been signed in accordance
   with [RFC7515].  Needed context could also be stored with the SET and
   retrieved with it.

6.  Privacy Considerations

   SET Transmitters should attempt to deliver SETs that are targeted to
   the specific business and protocol needs of subscribers.

   When sharing personally identifiable information or information that
   is otherwise considered confidential to affected users, SET
   Transmitters and Recipients MUST have the appropriate legal
   agreements and user consent or terms of service in place.
   Furthermore, data that needs confidentiality protection MUST be
   encrypted, at least with TLS and sometimes also using JSON Web
   Encryption (JWE) [RFC7516].

   In some cases, subject identifiers themselves may be considered
   sensitive information, such that their inclusion within a SET may be
   considered a violation of privacy.  SET Issuers and SET Transmitters
   should consider the ramifications of sharing a particular subject
   identifier with a SET Recipient (e.g., whether doing so could enable
   correlation and/or de-anonymization of data) and choose appropriate
   subject identifiers for their use cases.

7.  IANA Considerations

7.1.  Security Event Token Error Codes

   This document defines Security Event Token Error Codes, for which
   IANA has created and now maintains a new registry titled "Security
   Event Token Error Codes".  Initial values for the "Security Event
   Token Error Codes" registry are defined in Table 1 and registered
   below.  Future assignments are to be made through the Specification
   Required registration policy [RFC8126] and shall follow the template
   below.

   Error Codes are intended to be interpreted by automated systems;
   therefore, they SHOULD identify classes of errors to which an
   automated system could respond in a meaningfully distinct way (e.g.,
   by refreshing authentication credentials and retrying the request).

   Error Code names are case sensitive.  Names may not match other
   registered names in a case-insensitive manner unless the Designated
   Experts state that there is a compelling reason to allow an
   exception.

   Criteria that should be applied by the Designated Experts includes
   determining whether the proposed registration duplicates existing
   functionality, whether it is likely to be of general applicability or
   whether it is useful only for a single application, and whether the
   registration description is clear.

   It is suggested that multiple Designated Experts be appointed who are
   able to represent the perspectives of different applications using
   this specification in order to enable broadly informed review of
   registration decisions.  In cases where a registration decision could
   be perceived as creating a conflict of interest for a particular
   expert, that expert should defer to the judgment of the other
   experts.

7.1.1.  Registration Template

   Error Code
      The name of the Security Event Token Error Code, as described in
      Section 2.4.  The name MUST be a case-sensitive ASCII string
      consisting only of letters, digits, and underscore; these are the
      characters whose codes fall within the inclusive ranges 0x30-39,
      0x41-5A, 0x5F, and 0x61-7A.

   Description
      A brief human-readable description of the Security Event Token
      Error Code.

   Change Controller
      For error codes registered by the IETF or its working groups, list
      "IETF".  For all other error codes, list the name of the party
      responsible for the registration.  Contact information such as
      mailing address, email address, or phone number may also be
      provided.

   Reference
      A reference to the document or documents that define the Security
      Event Token Error Code.  The definition MUST specify the name and
      description of the error code and explain under what circumstances
      the error code may be used.  URIs that can be used to retrieve
      copies of each document at no cost SHOULD be included.

7.1.2.  Initial Registry Contents

   Error Code:  invalid_request
   Description:  The request body cannot be parsed as a SET or the Event
      Payload within the SET does not conform to the event's definition.
   Change Controller:  IETF
   Reference:  Section 2.4 of RFC 8935

   Error Code:  invalid_key
   Description:  One or more keys used to encrypt or sign the SET is
      invalid or otherwise unacceptable to the SET Recipient (expired,
      revoked, failed certificate validation, etc.).
   Change Controller:  IETF
   Reference:  Section 2.4 of RFC 8935

   Error Code:  invalid_issuer
   Description:  The SET Issuer is invalid for the SET Recipient.
   Change Controller:  IETF
   Reference:  Section 2.4 of RFC 8935

   Error Code:  invalid_audience
   Description:  The SET Audience does not correspond to the SET
      Recipient.
   Change Controller:  IETF
   Reference:  Section 2.4 of RFC 8935

   Error Code:  authentication_failed
   Description:  The SET Recipient could not authenticate the SET
      Transmitter.
   Change Controller:  IETF
   Reference:  Section 2.4 of RFC 8935

   Error Code:  access_denied
   Description:  The SET Transmitter is not authorized to transmit the
      SET to the SET Recipient.
   Change Controller:  IETF
   Reference:  Section 2.4 of RFC 8935

8.  References

8.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC2277]  Alvestrand, H., "IETF Policy on Character Sets and
              Languages", BCP 18, RFC 2277, DOI 10.17487/RFC2277,
              January 1998, <https://www.rfc-editor.org/info/rfc2277>.

   [RFC2818]  Rescorla, E., "HTTP Over TLS", RFC 2818,
              DOI 10.17487/RFC2818, May 2000,
              <https://www.rfc-editor.org/info/rfc2818>.

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246,
              DOI 10.17487/RFC5246, August 2008,
              <https://www.rfc-editor.org/info/rfc5246>.

   [RFC6125]  Saint-Andre, P. and J. Hodges, "Representation and
              Verification of Domain-Based Application Service Identity
              within Internet Public Key Infrastructure Using X.509
              (PKIX) Certificates in the Context of Transport Layer
              Security (TLS)", RFC 6125, DOI 10.17487/RFC6125, March
              2011, <https://www.rfc-editor.org/info/rfc6125>.

   [RFC6698]  Hoffman, P. and J. Schlyter, "The DNS-Based Authentication
              of Named Entities (DANE) Transport Layer Security (TLS)
              Protocol: TLSA", RFC 6698, DOI 10.17487/RFC6698, August
              2012, <https://www.rfc-editor.org/info/rfc6698>.

   [RFC7230]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Message Syntax and Routing",
              RFC 7230, DOI 10.17487/RFC7230, June 2014,
              <https://www.rfc-editor.org/info/rfc7230>.

   [RFC7231]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
              DOI 10.17487/RFC7231, June 2014,
              <https://www.rfc-editor.org/info/rfc7231>.

   [RFC7515]  Jones, M., Bradley, J., and N. Sakimura, "JSON Web
              Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
              2015, <https://www.rfc-editor.org/info/rfc7515>.

   [RFC7516]  Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)",
              RFC 7516, DOI 10.17487/RFC7516, May 2015,
              <https://www.rfc-editor.org/info/rfc7516>.

   [RFC7519]  Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
              (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
              <https://www.rfc-editor.org/info/rfc7519>.

   [RFC7525]  Sheffer, Y., Holz, R., and P. Saint-Andre,
              "Recommendations for Secure Use of Transport Layer
              Security (TLS) and Datagram Transport Layer Security
              (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
              2015, <https://www.rfc-editor.org/info/rfc7525>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8259]  Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
              Interchange Format", STD 90, RFC 8259,
              DOI 10.17487/RFC8259, December 2017,
              <https://www.rfc-editor.org/info/rfc8259>.

   [RFC8417]  Hunt, P., Ed., Jones, M., Denniss, W., and M. Ansari,
              "Security Event Token (SET)", RFC 8417,
              DOI 10.17487/RFC8417, July 2018,
              <https://www.rfc-editor.org/info/rfc8417>.

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.

8.2.  Informative References

   [RFC7235]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Authentication", RFC 7235,
              DOI 10.17487/RFC7235, June 2014,
              <https://www.rfc-editor.org/info/rfc7235>.

   [RFC8936]  Backman, A., Ed., Jones, M., Ed., Scurtescu, M., Ansari,
              M., and A. Nadalin, "Poll-Based Security Event Token (SET)
              Delivery Using HTTP", RFC 8936, DOI 10.17487/RFC8936,
              November 2020, <https://www.rfc-editor.org/info/rfc8936>.

Appendix A.  Unencrypted Transport Considerations

   Earlier versions of this specification made the use of TLS optional
   and described security and privacy considerations resulting from use
   of unencrypted HTTP as the underlying transport.  When the working
   group decided to mandate usage of HTTP over TLS, it also decided to
   preserve the description of these considerations in this non-
   normative appendix.

   SETs may contain sensitive information that is considered Personally
   Identifiable Information (PII).  In such cases, SET Transmitters and
   SET Recipients MUST protect the confidentiality of the SET contents.
   When TLS is not used, this means that the SET MUST be encrypted as
   described in JWE [RFC7516].

   If SETs were allowed to be transmitted over unencrypted channels,
   some privacy-sensitive information about them might leak, even though
   the SETs themselves are encrypted.  For instance, an attacker may be
   able to determine whether or not a SET was accepted and the reason
   for its rejection or may be able to derive information from being
   able to observe the size of the encrypted SET.  (Note that even when
   TLS is utilized, some information leakage is still possible; message
   padding algorithms to prevent side channels remain an open research
   topic.)

Acknowledgments

   The editors would like to thank the members of the SCIM Working
   Group, which began discussions of provisioning events starting with
   draft-hunt-scim-notify-00 in 2015.  We would like to thank Phil Hunt
   and the other authors of draft-ietf-secevent-delivery-02, upon which
   this specification is based.  We would like to thank the participants
   in the SecEvents Working Group for their contributions to this
   specification.

   Additionally, we would like to thank the following individuals for
   their reviews of the specification: Joe Clarke, Roman Danyliw, Vijay
   Gurbani, Benjamin Kaduk, Erik Kline, Murray Kucherawy, Barry Leiba,
   Yaron Sheffer, Robert Sparks, Valery Smyslov, Éric Vyncke, and Robert
   Wilton.

Authors' Addresses

   Annabelle Backman (editor)
   Amazon

   Email: richanna@amazon.com

   Michael B. Jones (editor)
   Microsoft

   Email: mbj@microsoft.com
   URI:   https://self-issued.info/

   Marius Scurtescu
   Coinbase

   Email: marius.scurtescu@coinbase.com

   Morteza Ansari
   Independent

   Email: morteza@sharppics.com

   Anthony Nadalin
   Independent

   Email: nadalin@prodigy.net